elisp - regexp-opt function missing in Emacs? -

elisp - regexp-opt function missing in Emacs? -

i've started playing around elisp create font-locks (syntax highlighting) in emacs. of tutorials out there mention using elisp function "regexp-opt" optimize regular expressions, version of emacs (23.2) doesn't seem have function. furthermore, googling reply doesn't seem turn useful results. ideas?

as can find out via c-h f regexp-opt:

regexp-opt compiled lisp function.

(regexp-opt strings &optional paren)

return regexp match string in list strings. each string should unique in strings , should not contain regexps, quoted or not. if optional paren non-nil, ensure returned regexp enclosed @ to the lowest degree 1 regexp grouping construct. returned regexp typically more efficient equivalent regexp:

(let ((open (if paren "\(" "")) (close (if paren "\)" ""))) (concat open (mapconcat 'regexp-quote strings "\|") close))

if paren `words', resulting regexp additionally surrounded \< , >.

note, function used in lisp code, not interactive command run m-x

emacs elisp